Hi,
Running OpenWRT 18.06 RC2 on x86/x64 machine, there is strange message at the end of dmesg log after booting.
[ 176.262358] random: crng init done
[ 176.262665] random: 1 urandom warning(s) missed due to ratelimiting
Any idea what it could be?
Everything seems to be working fine.
Many thanks,
1 Like
mbo2o
July 16, 2018, 5:53pm
2
Urandom needs some data to seed itself, try typing on the keyboard during boot give it more data
https://solus-project.com/forums/viewtopic.php?t=12086
2 Likes
It's really curious (the "solution" I mean).
Ansuel
July 17, 2018, 9:58am
4
Welcome to the magic world of entropy
4 Likes
[ 0.037905] random: get_random_u32 called from bucket_table_alloc+0x1a4/0x1f8 with crng_init=0
[ 5.369145] random: procd: uninitialized urandom read (4 bytes read)
[ 9.282518] urandom-seed: Seeding with /etc/urandom.seed
[ 9.994960] random: ubusd: uninitialized urandom read (4 bytes read)
[ 10.005219] random: ubusd: uninitialized urandom read (4 bytes read)
[ 10.011859] random: ubusd: uninitialized urandom read (4 bytes read)
[ 11.759376] urandom_read: 5 callbacks suppressed
[ 11.759383] random: jshn: uninitialized urandom read (4 bytes read)
[ 24.762525] random: fast init done
[ 57.390892] random: crng init done
Indeed!
https://wiki.archlinux.org/index.php/Random_number_generation
In computing, a hardware random number generator (HRNG), true random number generator (TRNG), non-deterministic random bit generator (NRBG), or physical random number generator is a device that generates random numbers from a physical process capable of producing entropy (in other words, the device always has access to a physical entropy source), unlike the pseudorandom number generator (PRNG, a.k.a. "deterministic random bit generator", DRBG) that utilizes a deterministic algorithm[2 Nature prov...
All this "improvements/changes" have been introduced in 4.14.XX Kernels?
Because I don't remember messages like that in older firmwares (Lede/OpenWRT 4.9.XXX).
juppin
July 18, 2018, 8:19am
7
You will see this messages also on 4.9, 4.4 and probably older kernel versions too.
Thanks @juppin I never realized about this messages before.
hnyman
July 18, 2018, 10:35am
9
Lack of entropy is a real problem in embedded devices right after boot.
I think that the warning for urandom quality was added to the kernel some time ago, but the warning was modified just a few months ago: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git/commit/?h=v4.14.56&id=4e00b339e264802851aff8e73cde7d24b57b18ce and backport to 4.9: https://lkml.org/lkml/2018/4/30/895
You might read Randomness quality for some background on lack of entropy in Openwrt. I wrote there a brief summary of mitigation attempts in Openwrt in the last 5-6 years.
2 Likes